$7lm - 5m - 3n + 4 = -8m + 5n + 1$ Solve for $l$.
Solution: Combine constant terms on the right. $7lm - 5m - 3n + {4} = -8m + 5n + {1}$ $7lm - 5m - 3n = -8m + 5n - {3}$ Combine $n$ terms on the right. $7lm - 5m - {3n} = -8m + {5n} - 3$ $7lm - 5m = -8m + {8n} - 3$ Combine $m$ terms on the right. $7lm - {5m} = -{8m} + 8n - 3$ $7lm = -{3m} + 8n - 3$ Isolate $l$ ${7}l{m} = -3m + 8n - 3$ $l = \dfrac{ -3m + 8n - 3 }{ {7m} }$